Quantum-well Distributed Feedback Lasers Research Articles

Strongly Detuned Tunable Photonic Oscillators

A semi-analytical dimensionless formula is presented for predicting the period-one frequency of an optically-injected laser over a wide range of injection powers and positive detunings. The result shows that for any given injected optical power, there exists an optimal detuning at which the period-one frequency is maximized. The formula is applied to a tabletop optical injection system with a commercially-available quantum-well distributed feedback laser with previously unknown design parameters. By extrapolating the linearity of the period-one frequencies at zero-detuning and weak-injection regimes, the physical control parameters of the laser are approximated to the analytical formula for wide ranges of injection powers and positive detunings. The accuracy of the model is experimentally verified, achieving period-one frequencies as high as 84.7 GHz.

43 Gb/s 1.3 $\mu$m DFB Laser for 40 km Transmission

We describe the performance of 1.3 $\mu$ m InGaAlAs ridge waveguide multiple quantum-well distributed feedback lasers. We obtained a 3 dB down bandwidth frequency of around 30 GHz by shortening the cavity length of the laser. We demonstrated experimentally that it is possible to obtain clear eye opening at a 43 Gb/s modulation speed after a 40 km single-mode fiber (SMF) transmission using a directly modulated laser. We fabricated a compact transistor outline (TO)-CAN module whose volume was about $1/19$ that of a conventional butterfly package. We successfully obtained clear eye opening for a 40 km SMF transmission at 43 Gb/s with the TO-CAN module.

Monolithic integration of electroabsorption modulators and tunnel injection distributed feedback lasers using quantum well intermixing

Electroabsorption modulators combining Franz-Keldysh effect and quantum confined Stark effect have been monolithically integrated with tunnel-injection quantum-well distributed feedback lasers using a quantum well intermixing method. Superior characteristics such as extinction ratio and temperature insensitivity have been demonstrated at wide temperature ranges.

Single contact monolithically integrated DFB laser amplifier

A monolithic 1550-nm single-mode AlInGaAs-InP multiple quantum-well distributed feedback laser and amplifier is presented. For the 400-/spl mu/m-long grating section /spl kappa/=112+ 30i cm/sup -1/, while the output is taken from the 200-/spl mu/m-long amplifier section. The slope efficiency of the chip was 0.21 W/A, while the kink free power from the fiber was 34 mW. Narrow linewidths of <50 kHz were measured, and the dispersion penalty remained less than 2.0 dB for a data rate of 2.5 Gb/s over 300 km of SMF-28.

Pulse tail suppression in laser diode outputby tunable notch filter

Efficient suppression of relaxation oscillations in the output signal from an overdriven gain-switched laser diode was demonstrated. Several quantum-well distributed feedback laser diodes from different manufacturers were used for experimental analysis. A five-fold increase in the peak power was achieved for the tail-free operation. It was found that spectral filtering removed the nonlinearly chirped components resulting in pulse shortening by a factor of three.

Amplified spontaneous emission model for quantum-well distributed feedback lasers

An amplified spontaneous emission model for quantum-well (QW) distributed feedback (DFB) lasers is presented, which takes into account local spontaneous emission, stimulated emission, and real refractive index change which are calculated from the Fermi-Dirac occupancy functions in a self-consistent manner. The local-normal-mode transfer-matrix method is used, which allows a coupling of the local DFB effect with the local QW spontaneous emission and gain. As an example, an analysis is given of a partly gain-coupled DFB laser with periodically etched QWs, which has a large discontinuity of spontaneous emission and gain in high- and low-corrugation regions. It is shown that the side-mode suppression improves with the increase of the number of etched QW's, due to the carrier-density-dependent gain-coupling.

Facet influence on wavelength tunability and linewidth chirp in InGaAs/InAlGaAs quantum-well distributed feedback lasers under high-bit-rate modulation

The strong influence of facet properties on wavelength shift and wavelength chirp is studied in uncoated and coated distributed feedback (DFB) lasers. A detailed comparison is performed between various experimental laser data (spectra, electronic and thermal wavelength tunability, relative intensity noise, linewidth) and the results of model calculations combining rate equations and the transfer matrix method. From experimental data of different lasers, a set of physical DFB laser parameters is determined. We succeeded in describing all the experimental data of different lasers by the same parameter set. By use of this set and a large signal analysis we found that the wavelength chirp and the wavelength shift resulting from electronic effects including spatial hole burning varies considerably for different end facet phases (EFPs) and facet coatings, but otherwise identical DFB laser geometry.

Thermal frequency drift suppression in tunable DFB lasers by plasma induced frequency shift enhancement

The authors propose enhanced-plasma-effect (EPE) lasers for coherent optical frequency division multiplexed networks. In the EPE lasers, the blue frequency shift due to the plasma effect is enhanced by incorporating a very thick p-side optical guide layer as a carrier reservoir for multiple quantum-well distributed feedback laser and it surpasses the red frequency shift due to the thermal effect. The results of demonstrating a frequency step response maintained in the blue shift region and an enhanced blue shift frequency modulation response over the whole modulation frequency range from DC are presented for the first time. >

Spectral linewidth reduction in partly gain-coupled 1.55 μm strained multiple quantum-well distributed feedback laser

The effective linewidth enhancement factor αeff and the spectral linewidth Δυ are reported for the first time for a partly gain-coupled distributed feedback laser with a gain corrugation in a strained multiple quantum-well active region emitting at 1.55 μm wavelength. The αeff value is estimated to be as low as 1 and is independent of the laser cavity length L, while a decrease in the linewidth-power product ΔυPo with L has been observed, with a measured linewidth of 2 MHz at 10 mW optical output power for 300-μm-long devices. The experimental results demonstrate that a small αeff is obtained due to the strain and the gain coupling effects, while further reduction of the spectral linewidth with L is the result of longitudinal index coupling effects.

Measurement of gain saturation coefficients in strained-layer multiple quantum-well distributed feedback lasers

Gain saturation coefficients of unstrained- and strained-layer multiple-quantum-well lasers were measured experimentally. These coefficients were higher in lasers that had compressive strain in their active-layer wells: 2.45*10/sup -17/ cm/sup 3/ with unstrained wells and 12.6*10/sup -17/ cm/sup 3/ with strained wells. The higher gain saturation coefficient in lasers with strained active-layer wells is related to their higher linear TE mode gain coefficient. The linearity factor (K factor) between a laser's damping constant and the square of the laser's resonant frequency decreased slightly with the introduction of the strain in the laser's active layer wells. This factor, however, took the value of about 0.2*10/sup -9/ s for each of these lasers.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

1.55 mu m gain-coupled quantum-well distributed feedback lasers with high single-mode yield and narrow linewidth

The fabrication and characteristics of gain-coupled 1.55- mu m GaInAlAs quantum-well metal-clad ridge-waveguide distributed-feedback lasers are discussed. The gain-coupling mechanism was provided by a thin ternary loss grating layer with an estimated gain-coupling strength of about 30/cm. For as-cleaved devices, the single-mode yield was as high as 70 and 95% for 600- and 800- mu m-long devices, respectively. Typical threshold currents were 40 and 55 mA, respectively. Both the high single-mode yield and the pronounced asymmetric spectra were calculated theoretically and give a strong indication that a significant amount of gain coupling was realized in the laser structure. For a 600- mu m-long device, a continuous-wave (CW) output power of 10 mW and a minimum linewidth of 1.6 MHz were measured. >

Gain saturation coefficients of strained-layer multiple quantum-well distributed feedback lasers

The gain saturation coefficients were measured for strained and unstrained multiple quantum-well distributed feedback (MQW-DFB) lasers. The gain saturation coefficient depends on the deviation of the laser's transverse-magnetic (TM) mode gain peak wavelength from its transverse-electric (TE) mode gain peak wavelength delta lambda , which is related to the strain on the active-layer wells. The gain saturation coefficient epsilon increased with increasing compressed strain on the active-layer wells. The coefficient epsilon of the unstrained MQW DFB laser with a wavelength deviation delta lambda of -350 AA was 2.45 x 10/sup -17/ cm/sup 3/, and epsilon increased up to 12.6 x 10/sup -17/ cm/sup 3/ in the SL-MQW DFB laser with a wavelength difference delta lambda of -890 AA.